Vehicles generally include opening/closing bodies such as electric window regulators, sunroofs, and sliding doors. When an opening/closing body is opened or closed using an electric drive motor, there are some regions where a driving force (torque) required for the opening/closing operation is larger than that required in other regions. For example, in an operation of opening a sliding door (opening/closing body), a large driving force is required at a fully open position since the sliding door is locked at this position to maintain the fully open state.
Accordingly, various structures for exerting a torque high enough to move the sliding door in the above-described operation have been suggested. For example, Japanese Unexamined Patent Application Publication No. 2003-301662 (FIG. 2) discloses a control apparatus including a drive motor (14) which switches between a low-speed mode for moving an opening/closing body with a relatively high torque at a low velocity and a high-speed mode for moving the opening/closing body with a relatively low torque at a high velocity. The control apparatus switches the mode of the drive motor (14) at a predetermined position and controls a voltage applied to the drive motor (14) such that the moving velocities of the sliding door before and after the sliding door reaches the predetermined position are substantially the same.
In this apparatus, the mode is switched depending on whether or not the sliding door has reached the predetermined position. Therefore, there is a risk that the drive motor cannot be adequately controlled when the sliding door receives load. For example, when a vehicle is on a slope, the sliding door receives load in the direction of inclination of the slope. Therefore, there is a risk that a torque high enough to lock the sliding door at the fully open position cannot be obtained at the final stage of the opening operation, where a large driving force is required.